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Title: heads with 42x37.5 valves Post by: Project_X on February 24, 2009, 17:20:38 pm Does anyone see a problem with running heads with these valves running them on like a combo of 74x85.5 or a 69x87?I can get the heads in standard bore, and also port and polishing is and option.Plus there in my price range if there ok to use?
If not, what kind of issues would I have?Its a daily driver, but I dont mind if its a high reving motor. Title: Re: heads with 42x37.5 valves Post by: Donny B. on February 24, 2009, 18:10:51 pm Not much room for that valve size with that small bore. Why not 94s where you will have plenty of room for the valves and can unshroud them so they flow well.
Title: Re: heads with 42x37.5 valves Post by: Project_X on February 25, 2009, 03:53:09 am I dont understand how theres not much room, when 87's are smaller than 94's. ???
Title: Re: heads with 42x37.5 valves Post by: Ohio Tom (DdK) on February 25, 2009, 04:06:35 am Those "large" valves in a "small" bore will be badly "shrouded" by the cylinder walls. Basically, the valves are very close cyl walls and actually impede "tulip" flow around the valve.
Personally, if you really want to stay with small bore (small displacement), then those valve sizes are way to large, even for a race motor. I have a 78 X 90.5 drag motor. It pulls past 8,200rpm. It only has 40 x 35.5 valve heads (with some serious port/chamber work). The point is this: You can get alot more flow thru smaller valves than you may think. Spend your money on portwork and you'll be better off. Just my opinion. Title: Re: heads with 42x37.5 valves Post by: Project_X on February 25, 2009, 05:53:36 am ok gotcha, but why do they make the heads with that size valves for the 85.5 bore then if it is not good for them?Can the large valves be used on the larger stroked 85.5 bore motors?
Like say 76x85.5, 78x85.5 an so on? Title: Re: heads with 42x37.5 valves Post by: stealth67vw on February 25, 2009, 05:57:26 am Your still gonna have the cylinder wall crowding the valves.
Title: Re: heads with 42x37.5 valves Post by: Project_X on February 25, 2009, 06:00:01 am ok lol i was just curious is all. By the way I was looking at the Mofoco 050 heads as a possibility. But I guess a set of there 043's with dual rev springs and a P&P will do.
On another note, can someone tell me what the point is in welding your heads? Title: Re: heads with 42x37.5 valves Post by: Bruce on February 25, 2009, 06:52:17 am .... but why do they make the heads with that size valves for the 85.5 bore then if it is not good for them? Because people buy them.Title: Re: heads with 42x37.5 valves Post by: stealth67vw on February 25, 2009, 07:15:29 am .... but why do they make the heads with that size valves for the 85.5 bore then if it is not good for them? Because people buy them.Title: Re: heads with 42x37.5 valves Post by: Tobi/DFL on February 25, 2009, 09:35:57 am ok gotcha, but why do they make the heads with that size valves for the 85.5 bore then if it is not good for them?Can the large valves be used on the larger stroked 85.5 bore motors? Like say 76x85.5, 78x85.5 an so on? ...why do they sell chromed engine tins? ;) ;D Title: Re: heads with 42x37.5 valves Post by: javabug on February 25, 2009, 13:25:59 pm .... but why do they make the heads with that size valves for the 85.5 bore then if it is not good for them? Because people buy them.Lots of money to be made from the "Bigger is Better" crowd. Title: Re: heads with 42x37.5 valves Post by: Project_X on February 26, 2009, 00:39:58 am .... but why do they make the heads with that size valves for the 85.5 bore then if it is not good for them? Because people buy them.Lots of money to be made from the "Bigger is Better" crowd. i guess im a part of that crowd lol |